1. Field of the Invention
The present invention relates to an optical detection and measurement system for locating a reflective surface plane and, more particularly, to an optical detection and measurement system which is capable of precisely locating individual reflective surface planes where multiple reflective surface planes may exist.
2. Background and Related Art
Various applications exist for locating a reflective surface plane. One application, for example, is in crystal growth. Other applications are in the deposition of materials whether opaque materials, such as certain metals, or translucent or transparent materials, as in the deposition of insulators or glassy material for passivation. Alternatively, applications exist for observing resist pattern films on a glass substrate, as in the process of manufacturing a liquid crystal substrate.
One of the difficulties in locating a reflective surface plane where transparent or translucent layers are involved resides in the fact that the multiple reflective surfaces produce multiple reflections which make it difficult to distinguish which reflection represents the surface of interest.
Various efforts have been made in the prior art to overcome the problem of distinguishing reflections from the top and bottom surface of glass, for example. Typical of the efforts for handling such reflections are those described in U.S. Pat. No. 5,317,142 to Noda, et al. and U.S. Pat. No. 5,483,079 to Yonezawa. However, the arrangements disclosed in these patents are complex and costly and are limited in their application.
In accordance with the present invention, a simple and precise optical detection and measurement system is provided which acts to deflect reflections from all surfaces except the surface of interest. The system allows detection of top surface position measurement of transparent materials, interlayer surface position measurement of transparent layers, determination of thickness of layers and end point detection in deposition, growth and like operations. Simplicity and accuracy is achieved in large part by using a divergent lens between the reflecting surfaces and a position sensing detector (PSD), such as, a quadrant detector.
Accordingly, it is an object of the present invention to provide an optical sensing system that can readily detect a single surface of an object.
It is another object of the present invention to provide an optical sensing and detection system that can monitor the surface change in material growth and depositions systems.
It is a further object of the present invention to provide an optical sensing system which is capable of precisely locating a given reflective surface plane.
It is yet another object of the present invention to provide an optical detection and measurement system which is capable of precisely locating individual reflective surface planes among multiple reflective surface planes.
It is still yet another object of the present invention to provide an optical detection and measurement system which is capable of precisely locating individual reflective surface planes in objects having more than one reflective surface plane to thereby measure the distance between planes.
It is a further object of the present invention to provide an optical detection and measurement system which is capable of precisely locating individual reflective surface planes in objects having multiple reflective surface planes so as to measure the distance between planes and thus the thickness of the layers between planes.
These foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings, wherein like reference members represent like parts of the invention.